This week in Their house, my garden, we visit a home grower of mushrooms, and chat to an expert about their ideal growing conditions.

I was sprawled on the carpet in the lounge, enjoying a sliver of sunlight and knitting, when I noticed a tall and slender little mushroom growing from the bottom of my pot plant. Fungi are no strangers to rental homes – on a Facebook post by a researcher asking for photos of mouldy flats, there are 388 replies, many of them horrific.

Liv Sisson, who has become New Zealand’s go-to expert for all things fungi, says “many New Zealand houses are ideal fungi-growing environs”. Why? Because fungi love dampness, just a little warmth, not much airflow, and indirect sunlight. One in five houses in New Zealand is damp, and that rate more than doubles if they’re rentals. Sisson herself has recently had mould grow on curtains in a flat. She wasn’t impressed when her landlord tried to withhold her bond on account of it.

Even Sisson the fungi obsessive would say that most fungi that grows by itself in a house would be harmful to your health, so do wipe it away with white vinegar. If it happens often, make a record of it and let your landlord know. If they don’t offer solutions, look into getting tenancy support, because it’s likely your home doesn’t meet Healthy Homes standards. 

Health hazards aside, the ideal fungi-growing environs we find ourselves living in could be harnessed to grow delicious edible mushrooms instead of toxic mould.

That’s exactly what Joe Trace has done. He rents a small Auckland flat with his partner, with a tiny garden that allows them to grow a few tasty herbs, like mint and rosemary, but not much in the way of food. By growing mushrooms, he’s found that “you can get a decent amount of food out of very little space”. 

Last Christmas, he received a Sporeshift grey oyster mushroom grow kit, which he describes as “pretty much like mycelium in a bag amongst a bunch of wood chips”. He popped it on a high kitchen shelf, sprayed it with water and a few weeks later little pins started emerging from the woodchip. Within a day they were the size of fingers, and a few days after, the size of hands.

Online reviewers have had similar experiences, saying “low effort with lots of reward”, “taste great, but watching them double in size each day is almost as fun as eating them”, and “just put it somewhere and it does its thing”. Nothing in my garden has ever grown so voraciously. 

Trace “very much enjoyed eating the mushrooms”, and he was hooked. Though the kits aren’t cheap, he reckons “it’s a deal” compared to supermarket mushrooms, because so many grow, and they taste better. Still, he wanted to get a bit more bang for his buck, and get a bit more involved than simply adding water. 

He went about some investigations online, and found a method to follow. He collected spores from the mushrooms and put what was left of the kit – a hunk of wood chips held together with a “bungee cord-like cotton candy” web of mycelium – into the worm farm. Mycelium is the colony of thread-like fungi from which mushrooms fruit as the reproduction mechanism. Then he mixed the spores into a slurry with sugar and water, let it incubate for a few weeks and “essentially infected a bunch of what’s called grains”. Grains are a substrate for mushrooms to grow, but we don’t need to worry about that because it went terribly. A lot of things grew, but most of them were not grey oyster mushrooms.

Trace noticed grey oyster mushrooms were instead growing out from the side of the worm farm. The remains were still alive. What came next “might sound a little bit gross”. He fished it all back out. Then he shredded cardboard, doused it in boiling water, let it cool, and gave it a squish to get the water out. In a 5-litre ice-cream container he made a “mycelium lasagne”, layering the broken up bits of old mycelium with his kind-of sterilised cardboard mush. Yum.

He knows that other domestic mushroom growers sterilise their cardboard using a pressure cooker, wear gloves and also sterilise everything with alcohol. It would probably increase his mushroom growing success, but also take some of the fun out of it. He does carefully wash his hands and any utensils used.

Trace then covered his lasagne, and left it on the top shelf for six weeks. During that time he made sure it was always damp, and not growing too many other funky things. He left one experiment too close to the stove top, and it grew colourful and mysterious fungi – he reckons that spot was too warm. The experiments left in cooler areas of the top shelf soon grew little needles. 

Trace hasn’t been able to grow as many mushrooms as the grow kit produced, but just this week made a vegetarian version of pulled pork with his home-grown mushrooms. He plans to add wood chips to his mycelium lasagne to help increase the crop.

His next experiment requires only shiitake mushrooms from the supermarket. The plan is to place a few gills down on tinfoil for a day. They will leave a print made out of spores, which could be dusty or slimy. Then, he will place that at the bottom of an ice-cream container and on top place some straw and shredded cardboard. As with the grey oyster mushrooms, he will keep it moist for about six weeks and wait for something to grow. If it works, it’s a mushroom kit for about $10. Or maybe it’s free, because surely the original mushrooms would be all good to eat afterwards?

Win your own Sporeshift splash and grow kit!

Sporeshift is a boutique mushroom farm in North Canterbury which is keen on building an environmentally friendly business and getting people to grow their own mushrooms in home gardens and indoors.

We have 10 of their 4kg grey oyster kits, which are perfect for beginners, to give away. To enter the draw, answer the following question: What conditions do mushrooms thrive in?

Email your answer, name and New Zealand mailing address, with “giveaway” in the subject line, to gabi@thespinoff.co.nz 

I will draw the winners on Monday morning. 

Top tip: For the best rewards it seems you can’t go wrong with a kit, but if you want to be gross and have more fun, experiment. Grey oyster mushrooms are beginner-friendly.

Task of the week: Welcome edible fungi into your home.